1. Field of the Invention
The present invention relates generally to a wireless power transmission system, and more particularly, to a method for controlling power of a power transmission transmitter.
2. Description of the Related Art
Wireless and contactless charging technologies have recently been developed and applied to many different electronic devices. The wireless charging technology, which uses wireless power transmission and reception, enables, for example, a battery of a cell phone to be automatically charged by placing the cell phone on a charging pad. The wireless charging technology does not require a separate charging connector. The wireless charging technology wirelessly charges electronic products and eliminates the need for a wired charger, thereby contributing to an electronic product's ability to be waterproof and portable.
In resonance method based charging, when a power receiver in need of charging is located in a power transmitter for transmitting wireless power, the power transmitter may charge the power receiver. If a plurality of power receivers is placed in a charging area of a single power transmitter, the power demanded from each power receiver may be different from the transmission power of the single power transmitter. Thus, charging for each power receiver needs to be conducted efficiently.
A conventional power transmitter establishes a voltage reference for power control to efficiently supply power to the power receiver. However, charging efficiency may vary depending on various charging conditions, such as, for example, characteristics of the power receiver, hardware design, a distance between the power receiver and the power transmitter, a charging position, etc.